Van-nette van bibber 1955 camper

please help-this is all i know about this. i want to know aactual year of manufacture.
the chassis is a 1955 second series TF(task force) 3800 1 ton dually chevrolet. thats the easy part. OEM was 235 inline 6 w/4spd and 5.13 ratio axle and 18" wheels.
it now sports SBC in front of stock 4spd and newer 19.5 wheels/radial tires since we use it. dont worry-i still have the OEM wheels.